Modern experimental and computational techniques are capable of determining bond lengths and angles with precisions of a few thousandths of an oangström and a few tenths of a degree. Such precisions are meaningful only if they are coupled with rigorous error analysis and careful evaluation of the physical meaning of the parameters.Here, internationally respected authors present all modern experimental and computational techniques for the determination of accurate molecular structures for the first time in one volume. They establish guidelines for accuracy requirements in answering broadly varying questions in current chemical research.